Thermoelectric switch



March 15 1927. F. s. DENiSON THERMO ELECTRIC swmcn .Filed Dec. 10, 1925 flrroRA/E Ya Patented Mar. 15, 1927.-

UNITED STATESPATE'NT OFFICE.

FREDERICK S. DENISON, OF MINNEAPOLIS, MINNESOTA, ASSIGNOR TO MINNEAPOLIS HEAT REGULATOR COMPANY, OF MINNEAPOLIS, MINNESOTA, A CORPORATION OF MINNESOTA.

THERMOELECTRIG SWITCH.

Application filed December 10, 1923. Serial No. 679,657.

This invention relates to improvements in thermoelectric switches of the general type useful for the control and regulation of heating plants or units by means of electric circuits. In such switches a thermo-bar 1S employed which is movable in response tethermal changes and thereby effects circuit changes controlling valves, dampers, blowermotors, other switches, and various other instrumentalities as is well understood in this art. This invention more particularly includes improvements in the usual make-andbreak devices of such thermo-electric switches which function upon what is generally known as the snap principle. A

thermostatic switch of this general type is shown in the prior patent of the inventor hereof, No. 1,390,987 of September 20, 1921.

The object therefore of this invention 1s to provide an improved thermo-electrlc switch.

Other objects of the invention w1ll more fully appear from the following description and the accompanying drawings and will be pointed out in the annexed claims.

In the drawings, there has been disclosed a structure designed to carry out the ob ects of the invention but it is to be understood that the invention is not confined to the exact features shown as ,various changes may be made within the scope, of the claims which follow.

In the drawings:

Figure 1 is a plan view of the switch and base with the cover removed;

Figure 2 is a vertical section through the switch; and

Figure 3 is a fragmentary enlarged detail view, partially in section, to show the assembled relation of the contact-finger and thermo-bar.

The switch includes a metallic base 4 and a suitable cover 5 adapted to enclose the working parts. The thermo-bar comprlses a substantially ring-like portion 6 and an i elongated bar 7 extending downwardly above the base which is preferably mounted in an upright position as, for example, upon a wall. The ring-like portion 6 1s carried'by a post 8 mounted upon the base and adapted so for connection within a. circuit as 15 wellunderstood in this art. Two opposing abutments or points 9 and 11 are supported by the base. One of these points may be in electrical connection with a wire 12 and the other may function as a simple abutment;

or, as here shown, each may be in electrical connection with a wire 12 as is well understood in this art. In order that the positions of the two points 9 and 11 may be selectively varied with relation to the thermo-bar 7, they are preferably supported for movement upon the base.

An elongated plate 13 is mounted at its upper end upon the pivot pin 14 carried by the base. Downwardly extending from its pivotal axis, the plate is formed with an outwardly ofi'set portion 15, then a transversely enlarged section 16 and finally a terminal foot 17 having a toe 18 bent to extend through an aperture 19 extending partly across the base and to engage frictionally the under surface of the base adjacent the aperture 19. The selected means for shifting the plate is a lever 21 pivoted upon the in 22 outwardly projecting from the base eneath the offset portion 15 which portion is apertured to receive. the stud 23 of the lever 21. This stud 23 is embraced by an elongated U-shaped wall 24. secured to the outer face of the offset portion 15 of the plate so that movement of the lever 21,.is communicated to the pivoted plate in a lessened degree. The lower end of the lever 21 terminates in an indicator 25 which co-operates with temperature indicia upon the outer surface of the bridge 26 projectingfrom the lower portion of the base 4:. I

The opposing contact points 9 and 11 are carried by the enlarged section 16 of this movable plate. Each point is mounted upon a post 27 carried by, and extending through, the section 16. The rear end of each post is suitably connected to a wire 28 in electrical connection with the binding posts 29 and therefore with the wires 12, in accordance with the usual practice in this art.

A contact finger is provided to oscillate between the two opposing abutments or points in order to make and break a circuit through the single live contact when one is merely an abutment or to effect electrical contact with either point when each is live. This finger is movable in response to the thermal changes in the thermo-bar thereby to regulate or control the circuits and the instrumentali'ties of various types incorporated therein. This finger is mounted to function upon the snap principle and, in the preferred form shown, consists of a piece of sheet metal provided adjacent its lower abuts against this wa end with a metallic contact 31 and at face of the wall. The finger is held in such awembled operative relation by means of a coil spring 36 connected at one end to the thermo-bar 7 and at its other end to the finger. This operative mounting of the finger .assures a sensitive response to movements of the bar 7. Y

The spring 36 is arranged so that it passes through the pivotal axis of the finger during oscillatory movements of the thermo-bar and thus snaps the finger against and away from the two opposing contact points. The

wall 33 is formed with an elongated transverse 0 ning 37 through which the spring passes om the thermo-bar connection between the forks of the finger to the base thereof where the spring-end is inserted through and turned about a hole. in the finger. The two forks 32- straddle this openus, when the thermo-bar 7 moves from its full-line position, shown in Figure 3, to its dotted-line osition, the sprin is placed under increased tension because -t e pointed support of the finger causes the distance between the bar-end and the base of the forks to be relatively increased. As the thermobar continues its swing beyond the line of centers this increased sprin -tension is'added to the normal tension 0 the spring and results in a quick and sudden snap of the contact end of the finger from one point to the other. It may also be noted that movement of the indicator 25 functions to move the two contact points and the finger with relation to the thermo-bar which is mounted upon the base so that the same expandedor contracted state of the thermo-bar will effect different positions of the finger with relation to the two points.

Having thus described my invention what I claim as new and desire t'isecure by Letters-Patent, is:

1. A. device of the class described comprising a base, a thermo element. thereon, a plate pivoted to the base and having a pair of contacts, a finger carried by and rockably engaged with said -pivoted plate, and arranged between the' contacts, and a tension element connecting the finger and thermoelement and holdin said finger rockably engaged on its mova e supporting plate.

2. A device of the class described comprising a base, a thermo element thereon, a plate pivoted to thebase and having a pair of contacts, and a finger rockably engaged with the pivoted plate and extending between the contacts, and a tension element connecting the finger and thermo-element to hold the linger rockably engaged with its movable supporting plate.

3. In a t ermo-electric switch, a makeand-break device including in combination with opposing abutments. a base, a plate movably mounted. on the base, a contactfinger pivotally engaging the plate and adapted to oscillate to effect electrical contact with one of said abutments, a. thermobar mounted on the base, a spring connected to the thermo-bar and finger and holding the latter in oscillatory position, the spring being arranged to pass through the pivotal axis of the finger upon movement of the thermo-bar thereby to snap the finger from one abutment to another, means for shifting the movable plate whereby the pivotal action of the finger is changed with relation to the thermo-bar.

4. A device of the class described comprising a base, a plate pivoted thereto and having contact members and a finger rockably engaged with the plate and extending between the contacts, a thermostatic element carried by the base, a spring connecting said thermo-element and finger,'a lever pivoted to the base beneath the plate, a connection between the plate and lever, a bridge formed upon the base over the end of the lever and carrying indicia. the lever havin a po' ter ada te to register with said in 'cia w on the ever is shifted.

5. In a thermo-electric switch, a makeand-break device including in combination, abase, a plate movably mounted 'upon the base, opposing electric contact points upon the plate, a contact-finger pivotally engagin the plate and adapted to oscillate .to e ect electrical contact with either point, a

Ill)

thermo-bar on the base, a spring connected'to the thermo-bar and finger to hold the latter in oscillatory position, the spring being arranged to pass through the pivotal "axis of the finger upon movement of the thermo-bar thereby .to sna the. finger from one contact point to anot er, means for shifting the movable plate whereby the positions of the contact points and finger may be changed with relation tothe thermo-bar.

6. Ina thermo-electric switch, a makeand break device, including in combination with opposing electric contact points, a base, a supporting plate movably mounted upon the base, a thermo-bar mounted upon the base and extending toward the contactpoints, a head pro ecting from said plate adjacent the end of the thermo-bar, the

head havinganaperture therein, a contact.

finger having terminal forks engaging said head u on each side of the aperture, the finger eing adapted to oscillate to efiect electric contact with either point, a spring connected to the thermo-bar and finger to hold the latter against the head in oscillatorv position,-the 5 ring passing throu h the aperture in the ead and between t e forks of the finger and adapted to pass through the pivotal axis of the finger upon movement of the thermo-bar to snap the finger from one contact point to another.

7. A device of the class described comprising a base, a plate pivoted thereto and having contact members and a finger rockably engageo with said plate and extending between the contacts, a thermostatic element carried by the base, and a spring connecting the thermo element and finger, a lever pivoted to the base, an elongated substantially U-shaped projection on the plate, and a lug on the lever disposed in the projection, whereby movement of the lever shifts the plate differentially.

In witness whereof, I have hereunto set my hand this 15th day of August 1923.

FREDERICK S. DENISON. 

